Method for displaying gray scales of image display unit

Abstract

A gray scale display method includes converting the binary code of conventional picture data into an optimal code, based on display system characteristics. Gray levels of an image to be displayed are error-diffused and displayed using frame rate modulation. In order to reduce the likelihood of saturation of the gray levels, the maximum value of data displayed according to the optimal code is greater than or equal to the maximum value of the picture data displayed according to a conventional binary code. In addition, the number of adjacent gray levels is minimized. As a result, the driving voltage for driving electrodes in a display device and picture cross talk are reduced.

What is claimed is: 
     
       1. A method for displaying gray scales of an image display unit, comprising the steps of: determining an error diffusion processing value of input picture data of N bits as n bits which is less than N;   converting said picture data of N bits into the optimal data code of M bits which is larger than or equal to N and is composed of a picture data code of (M-n) bits selected to satisfy the first standard for selecting the code wherein the maximum value of the data of the upper (M-n) bits displayed by the optimal code system should be equal to or larger than the maximum value of the picture data displayed according to the binary code system and the second standard for selecting the code wherein, among the new gray levels generated by the error diffusion method, the number of adjacent gray levels should be smallest and an additional code of n bits for space modulation;   error-diffusion-processing the n bits of said error diffusion processing value among the picture data which are converted into said optimal M bits; and   displaying the picture data code of said (M-n) bits wherein said n bits undergo error diffusion processing as a picture.   
     
     
       2. A method for displaying gray scales of an image display unit as claimed in claim 1, wherein said step for converting said picture data of N bits into the optimal data code of M bits is performed to satisfy the third standard for selecting the code, wherein the optimal code system should minimize the difference of the weighting values of the data values between the most significant bit and the least significant bit and the fourth standard for selecting the code, wherein the optimal code system should minimize the difference of the weighting values between the respective data bits when there exist more than two code systems which simultaneously satisfy said first and second standards for selecting the code. 
     
     
       3. A method for displaying gray scales of an image display unit as claimed in claim 1, wherein the gray scales of said picture data code of (M-n) bits are displayed using the voltage amplitude modulation method or the voltage and frame rate modulation method in said step for displaying said picture. 
     
     
       4. A method for displaying gray scales of an image display unit as claimed in claim 2, wherein the gray scales of said picture data code of (M-n) bits are displayed using the voltage amplitude modulation method or the voltage and frame rate modulation method in said step for displaying said picture. 
     
     
       5. A method for displaying gray scales of an image display unit, comprising the steps of: determining an error diffusion processing value of input picture data of N bits as n bits which is smaller than N;   converting said picture data of N bits into the optimal data code of M bits which is greater than or equal to N bits and composed of a picture data code of (M-n) bits selected to satisfy the third standard for selecting the code, wherein the optimal code system should minimize the difference of the weighting values of the data values between the most significant bit and the least significant bit and the fourth standard for selecting the code, wherein the optimal code system should minimize the difference of the weighting values between the respective data bits, and an additional code of n bits for a space modulation;   error-diffusion-processing n bits being said error diffusion processing value among the picture data which are converted into said optimal M bits; and   displaying the picture data code of said (M-n) bits wherein said n bits undergo the error diffusion processing as a picture.   
     
     
       6. A method for displaying gray scales of an image display unit as claimed in claim 5, wherein said step for converting said picture data of N bits into the optimal data code of M bits is performed to satisfy the first standard for selecting the code, wherein the maximum value of the data displayed by the optimal code system should be equal to the maximum value of the picture data displayed according to the binary code system and the second standard for selecting the code wherein, among the new gray levels generated by the error diffusion method, the numbers of adjacent gray levels should be smallest, when there exist more than two code systems which simultaneously satisfy said third and fourth standards for selecting the code. 
     
     
       7. A method for displaying gray scales of an image display unit as claimed in claim 6, wherein the gray scales of said picture data code of M-n bit are displayed using the voltage amplitude modulation method or the voltage and frame rate modulation method in said step for displaying said picture. 
     
     
       8. A method for displaying gray scales of an image display unit as claimed in claim 5, wherein the gray scales of said picture data code of M-n bit are displayed using the voltage amplitude modulation method or the voltage and frame rate modulation method in said step for displaying said picture.